This invention relates to a process for preparing amines from alcohols.
Amines find utility as dispersants, surfactants, chelants, catalysts, curing agents, extenders in polyurethanes, and as starting materials in the preparation of pesticides.
It is well-known that aliphatic amines can be prepared by the reaction of an alkyl halide with ammonia or a reactant amine. The product is an amine hydrohalide salt, which must be neutralized with base in order to recover the valuable amine product. The neutralization produces a waste stream of metal salt, which must be removed. Moreover, the process yields primary, secondary, and tertiary amines, and is therefore not selective.
It is also well-known that aromatic amines can be prepared by the reaction of an aryl halide with ammonia or a reactant amine. This process requires harsh reaction conditions, and selectivity is therefore reduced.
It is known to employ catalysts comprising an oxide of a Group VIB metal in the direct amination of alcohols. For example, U.S. Pat. No. 4,206,150 discloses the reaction of alcohols with ammonia, primary or secondary amines in the presence of a catalyst comprising a mixture of components selected from the groups consisting of copper, copper oxide and mixtures thereof, and molybdenum oxide, tungsten oxide and mixtures thereof.
Japanese Patent No. 48-96475 (1973) discloses the use of tungsten oxide in combination with zirconium oxide or titanium oxide in the amination of hydroxybenzenes by ammonia.
Likewise, U.S. Pat. No. 3,491,148 discloses the amination of mixtures containing n-amyl alcohol and cyclopentanol by ammonia in the presence of a catalyst containing cobalt or nickel, optionally in admixture with a variety of metals including tungsten, preferably, as the oxide.
U.S. Pat. No. 3,714,259 discloses a process for producing linear polyethylenepolyamines comprising reacting an ethyleneamine with an ethanolamine in the presence of a catalyst in the form of oxides of chromium, copper, nickel or cobalt.
The Group VIB metal oxide catalysts identified hereinbefore are prone to sintering during the amination reaction, especially at elevated reaction temperatures. Sintering is a process wherein particles of the catalyst diffuse and agglomerate. Consequently, sintering lowers the surface area of the catalyst and plugs the pores of catalyst supports. Disadvantageously, the catalyst which has sintered usually exhibits a lower catalytic activity.
It would be desirable to have a catalyst which is active and selective in the direct amination of alcohols to amines. It would be more desirable if the catalyst does not sinter at elevated temperatures. Such a catalyst could be operated for prolonged periods of time at elevated temperatures without loss of catalytic activity.